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Título: | Dynamic behavior in solution of the trans-hydridodihydrogen complex [OsHCl(ν2-H2)(CO)(PiPr3)2]: Ab initio and NMR studies |
Autor: | Bakhmutov, Vladimir I.; Esteruelas, Miguel A. CSIC ORCID; Lledós, Agustí; Modrego, Francisco J. CSIC ORCID; Oro, Luis A. CSIC ORCID; Sola, Eduardo CSIC ORCID CVN | Fecha de publicación: | 1996 | Editor: | Wiley-VCH | Citación: | Chemistry - A European Journal 2(7): 815-825 (1996) | Resumen: | Reaction of complex [OsHCl-(CO)(PiPr3)2] (1) with hydrogen gives the trans-hydrodidodihydrogen complex [OsH-Cl(π1-H2)(CO)(PiPr3)2] (2). The H-H distance in the dihydrogen ligand, determined by variable- temperature 1H T1 measurements, is 0.8 Å. The fast-spinning nature of the dihydrogen ligand of 2 has been deduced by evaluating the deuterium quadrupole coupling constant for the π2-D2 ligand of [OsDCl(π2-D2)(CO)(PiPr3)2] ([D3]2). Measurements of the equilibrium constants for formation of 2 (K) give ΔH(±) = -14.1 ± 0.5 kcal mol-1 and ΔS(±) = -30 ± 1 e.u. An equilibrium isotope effect K(d)/K of 2.8 is found for this reaction. The activation parameters for the H2 loss from 2 are ΔH(±) = 14.6 ± 0.2 kcal mol-1 and ΔS(±) = 9.9 ± 0.5 e.u. Hydrogen exchange between the hydrido and π2-H2 ligands of 2 takes place at a slow rate (k2/(obs)) at high temperatures. Activation parameters ΔH(±) = 17.4 ± 0.5 kcal mol-1 and ΔS(±) = 1.3 ± 1 e.u., and a kinetic isotope effect (k2/(obs)/k(2d)/(obs)) of 4.6 at 333 K have been determined for this exchange. Ab initio calculations on the model system [OsH- Cl(H2)(CO)(PH3)2] confirm that the trans-hydridodihydrogen complex [OsH- Cl(π2-H2)(CO)(PH3)2] (4) is the most stables species (r(HH) = 0.84 Å). In addition, a cis-hydridodihydrogen complex 5, with a relative energy of 13.8 kcal mol-1, occupies a local minimum in the potential hypersurface. The energy of other possible trihydrido isomers have also been evaluated. On the basis of the thermodynamic and kinetic data, and the results of the ab initio calculations, the possible mechanism for the H/π2-H2 exchange is discussed. | URI: | http://hdl.handle.net/10261/64576 | DOI: | 10.1002/chem.19960020714 | Identificadores: | doi: 10.1002/chem.19960020714 issn: 0947-6539 e-issn: 1521-3765 |
Aparece en las colecciones: | (ICMA) Artículos |
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